Study of self-diffusion in dense hydrogen gas by quasielastic incoherent neutron scattering

Abstract

Incoherent quasielastic scattering of neutrons from hydrogen gas has been measured at room temperature and 78°K in a range of pressures from 100 to 2000 atm. We present in some detail the data-reduction procedure which allows us to extract the van Hove self-correction function $S_s(Q, \omega )$. We then extract the linewidth of the self-correlation function by assuming a Lorentzian line shape. By extrapolating to the small-$Q$ limit, we obtain the macroscopic self-diffusion coefficient as a function of density and temperature. We compare the results with the hard-sphere Enskog theory and conclude that there is considerable enhancement over the Enskog values at higher densities.